Lubricating oil refining



C. E. ADAMS LUBMCATING OIL REFINING Feb. 16,1937.

Filed May 10, 193

@MASK ATTORNEY Patented Feb. 16, 1937- UNlrEo STATES 2,070,567 LUBRICATING om REFINING Y Chester E. Adams, Hammond, Ind., assignor to Standard Oil Company, Chicago, Ill., a corporation of Indiana Application-May 10, 1.935, Serial o. 20,878`

14 Claims.

This invention relates to the refining of lubricating oils and more specifically to the refining of lubricating oil stocks by`oxidizing some of the constituents and then removing the oxidation products by treatment with a normally gaseous hydrocarbon such as propane preferably at a temperature in the vicinity of the critical temperature of the normally gaseous hydrocarbon. It also relates to the production of asphalt.

It is an object of my invention to provide an/ efficient and economical process forvthe production of lubricating oils having improved qualities with respect to temperature coefficient of viscosity, volatility, color, sludge stability, 15 etc. It is also an object of my invention to provide an improved process for the manufacture of asphalt. Other and more detailed objects of my invention will become apparent as the description thereof proceeds.

It has found that when a lubricating oil stock f is drastically oxidized many'or most of its less desirable constituents are converted into oxidation products, while most of its more valuable constituents remain unoxidized. The oxidation method is therefore a valuable method of r'ening lubricating oil stocks provided only that eiicient means can be found for the removal of the oxidation products. I have found that. these oxidation products can be removed from the unoxidized hydrocarbons more completely and more efficiently by precipitation with propane or similar normally gaseous hydrocarbon at relatively high temperatures, i. e. at temperatures frin the vicinityl of the critical temperature'of'the normally gaseous hydrocarbon, than in any other known manner.

As compared for example with removal of the oxidation products with propane at relatively low temperatures, high temperature propane treatment gives an oil having a lower temperature coefficient of viscosity, a higher volatility, a lower carbon-forming tendency, and a better color.

My invention is applicable to any type of hydrocarbonl lubricating oil stock sinceall such. 45 stocks are composed of various constituents which differ materially in the ease with which they can be oxidized and since in general the more readily oxidizable constituents are the less desirable constituents from the lubricating oil standpoint. Furthermore the oxidized products are quite uni.. formly less soluble in propane and similar nor- -mally gaseous hydrocarbons at high temperatures than the unoxidized hydrocarbons. My invention is, however, particularly applicable to Cil , and it is particularly useful at temperatures of Mid-Continent and other mixed base lubricating oil stocks which contain largel quantities of difficulty oxidizable relatively paraifinic hydrocarbons and which also contain considerable quantities of the less desirable and relatively readily 5 ozxidizable hydrocarbons of a relatively nonparafllnic nature. e

In the oxidation step of my process I can use any oxidizing agent which will give selective oxidation of the relatively non-parainic hydrocarbons but I prefer to use air or other oxygencontaining gas. The temperature ofthe oxidation is subject to .wide variation. In general, the desired oxidation can be accomplished at temperatures as low as 200 F., but I prefer to use temperatures at least as high as 250 F. and still more preferably, temperatures in the approximate range 300\F. to 400 F. in order to secure more rapid and eicient oxidation. Oxidation temperatures as high as 500 F. or even higher can be used but the oxidation obtained at these temperatures is somewhat less selective than that obtained by the use of lower temperatures. In any event the oxidation 'temperature` should be below that at which substantial cracking occurs.

Various catalysts can also be used to expedite the oxidation reaction and to render it more selective. Ferrie chloride is my preferred catalyst 250350 F. Quantities-of catalyst of the order v of magnitude of 1% of the weight of thev lubricating oil stock are suitable. However, amounts of from 0.1% to 10% orv more may be used.

The time of oxidation will depend upon the character of the stock, the character of the product desired, the oxidizing agent chosen, the presence or absence of a catalyst, the degree of intimacywith which the oxidizing agent is contacted withthe stock and particularly the temperature of the material undergoing oxidation. Using air as the oxidizing agent in the absence of a catalyst and with intimate contact between the oxidizing agent andthe stock being oxidized, the oxidation time at a temperaturev of between 300 F. and 400 F. maysuitably be from 30 to '24)0 hours. At lower temperatures longer times will be required to obtain the same degree of oxidation, while at highertemperatures the time of contact need not be as long. vIn any event, the oxidation step of my process should produce drastic oxidation for the purpose of removing a substantial portion of the undesired constituents of low temperature coefficient of viscosity 55 and not merely superficial oxidation for color removal, improvement in `sludge stability, removal of volatile materials, etc. I prefer, in general,

that the oxidation be sufciently drastic to conbe said that the lubricating oil produced by the oxidation and propane (or other normally gaseous hydrocarbon) treatment steps of my process should have a Viscosity index at least 10 and preferably at least 15 Dean and Davis units higher than that of the stock charged to my process.

The degree of oxidation to be effected in any case will depend somewhat on the nature of the stock used as well as on the characteristics of the product desired. For Pennsylvania lubricating oil stocks, the oxidation may suitably convert about 5% to about 10% or more of the soluble material in the stock into materials insoluble in propane or similar material under the conditions of my process. The degree of oxidation, similarly defined, for a Mid-Continent lubricating oil stock may suitably be from about 15% to about 30% or higher and for a Coastal lubricating oil stock from about 20% to about 40% or higher.

Following the oxidation step, the oxidized products together with the unoxidized portion of the stock is agitated or otherwise contacted with a normallygaseous hydrocarbon. I prefer to use propane in most cases. However, the use of ethane is sometimes advantageous, particularly when it is desired to produce a relatively volatile and nonviscous lubricating oil. Isobutane and normal butane can also be used, particularly in the manufacture of heavy lubricating oils. It is also possible to use the olenic hydrocarbons corresponding to the foregoing parainic hydrocarbons but they are not as eflicient. Mixtures of these various hydrocarbons can be used but I prefer to use a single relatively pure hydrocarbon. The quantity of normally gaseous hydrocarbon used may suitably range from 2 volumes of normally gaseous hydrocarbon per Volume of material undergoing treatment up to l0 volumes or even more normally gaseous hydrocarbon per volume of' material undergoing treatment. I prefer, however, to use from about 4 to 8 volumes of normally gaseous hydrocarbon per volume of 'material undergoing treatment.

The temperature used in the case of propane should be at least F. and preferably at least F. For other normally gaseous hydrocarbons, the temperature should have a similar relation to the critical temperature of the normally gaseous hydrocarbon and, in general, the mini- 'mum temperature of the normally gaseous hydrocarbon treatment should be about 80 F. below and preferably about 50 F. below the critical temperature of the light hydrocarbon used.

As to the upper limit of the temperature useful in this step of my process, I prefer to operate at a temperature at least 10 F. below the critical temperature of the normally gaseous hydrocarbon used. It is possible, however, to operate at the critical temperature or even considerably above the critical temperature. The critical temperature in the case of propane is approximately The pressure used in the normally gaseous hythe propane or other normally gaseous hydrocarbon in the liquid state.

In operating at temperatures above the critical temperature this is obviously impossible and in these cases the pressure should be sufficiently high to givea density of the` order of magnitude of that which the same system would have in the liquid state in the vicinity of the critical conditions. Normally gaseous hydrocarbons when in the liquid state or when in the high pressure, high density condition referred to in the last sentence are referred to in the appended claims as condensed.

Following the precipitation of oxidation products by the use of normally gaseous hydrocarbon and removal of the normally gaseous hydrocarbon from the unoxidized oil, other refining steps may and usually should be used. These subsequent rening steps are particularly useful in order to enhance the sludge stability and color of the finished lubricating oil. Acid treating, clay treating, solvent extraction and dewaxing arev among the finishing steps whichmay suitably be used, individually or in combination.I I prefer in general that these steps follow the normally gaseous hydrocarbon treatment but it is to be understood that some of them may precede 4the oxidation step and/or be interposed between the oxidation and normally gaseous hydrocarbon treatment steps without departing from the spirit of my invention.

I prefer to finish the oxidized and normally gaseous hydrocarbon treated oil by dewaxing, if necessary, followed by low temperature sulfuric acid treating, preferably in light hydrocarbon solution and/or clay contacting.

One particularly advantageous sequence of steps is to chill the solution of processed oil discharged from the high temperature separation step to a dewaxing temperature, for instance -40 remove the wax, and then treat with sulfuric acid preferably at a relatively low temperature, for instance 20 F., yvhile still in normally gaseous hydrocarbon solution. This low temperature acid treating in normally gaseous hydrocarbon solution gives a finshedoil of parn ticularly good color.

perature was raised to F. The bomb, which' was mounted on trunnions and equipped with side-draws, was rotated for a short time and then allowed to stand still vwhereupon the insoluble oxidation products settled to the bottom, the supernatant solution of unoxidized processed oil was drawn off through the appropriate sidedraws and propane was flashed off. The processed oil was found to have a viscosity of 86,4 seconds. Saybolt at 210 F. and a color of 23/4 (15% oil in 85% water white kerosene-Tag-Robinson method). The yield up to this point was 53%. This oil was then dewaxed, yielding an oil having a viscosity of 92.6 seconds Saybolt at 210 F. and a viscosity index of 83.4 (14.4 units higher than that of the stock). After treating with onehalf pound of 98% sulfuric acid per gallon of oil in hexane solution at 20 F., the finished oil had a viscosity of 82.2 seconds Saybolt at 210 F. and a viscosity index of 89.1.

Examples II and IIL-A Mid-Continent distillate having a viscosity of 124 seconds Saybolt at 210 F. anda viscosity index of 65 was placed in a still and blown with air for 26 hours at 450- 475`F. without a catalyst. The material from the oxidation still wasl divided into twoportions, each of which was treated with 5.7 times its volume of propane in the manner described above. 'Ihe temperature of the propane treatment varied in the two cases and the results were as follows:

It will be noted that although the treatment at the higher temperature (Example III) gave a somewhat lower yield, it gave an oil markedly superior to that produced by the lower temperature treatment (Example II). This superiority included viscosity index,`color and viscosity. The

lower viscosity in Example III indicates a more volatile oil having lower carbon-forming tendencies.

Each of these oils was dewaxed and then percolated through 'clay without acid `treatment.

- Both oils were percolated to a finished oil color of 31/2-4 N. P. A. The oil of ExampleII gave a percolation yield of 75 gallonsof oil per ton of clay while under identical conditions with the same clay the oil of Example III gave a yield of 154 gallons per ton. This is another indication of the superiority -of the higher temperature treatment.

This superiority is much morel marked when compared with propane treatment at atmospheric or sub-atmospheric temperatures.

I will now proceed to outline a preferred method of operating my process. This method will be described in conjunction with the accompanying `drawing in the form of a flow diagram which forms provided with bailles not shown. Air, oxygen or other oxidizing agent is introduced into this tower through line i5 and ultimately passes out through v vent it. This counter-current oxidation is preerred but it will be understood that a simple batch process can be used. Furthermore, a battery of these oxidizers I3 can be used in series in order to increase the oxidation time.

` The materialr from the oxidation steppasses out of oxidizer I3 through line Il into surge tank I8 from which it is pumped by pump I9 through heater or cooler 20 into asphalt precipitator 2|'.

In precipitator 2| the material from the oxidation step is passed counter-current to propane or similar normally gaseous hydrocarbon which is introduced through line 22 in a manner hereafter to be described. The propane passes upward and dissolves the unoxidized constituents from the oxidation step. It may also dissolve some of the oxidized constituents. The insoluble material which passes out of precipitator 2| through line 23 constitutes a superior asphalt-(even though the original stock was completely asphalt free) and the characteristics of this asphalt can be closely controlled by controlling the degree of precipitation in precipitator 2|. 'I'his in turn is a function of the temperature and pressure existing in precipitator 2| and of the ratio of propane or other normally gaseous hydrocarbon to the material being treated. When operating in my preferred temperature and pressure range immediately below the critical conditions of the propane or other .normally gaseous hydrocarbon the amount of precipitation willvary directly with the temperature and indirectly with the pressure. When operating at atmospheric or sub-atmospheric temperatures, however, the amount of precipitation will vary indirectly with the temperature and the pressure will have little eect on the degree of precipitation so long as it is sufficient to maintain liquid phase conditions.

At low temperatures the asphalt withdrawn from the bottom of extractor 2| may be a plastic solid and require the use of a conveyor inthe place of conduit 23.

By simple control of the aforementioned variables in precipitator 2| an asphalt of any desired specifications can be obtained. A batch precipitator or a multi-stage counter-current precipitator can, of course, be used.

The asphalt from the precipitator passes through a heater 24 (which may in many cases be omitted) into a flash tower 25 which may if necessary be heated at its baseby coil 23. Prov 2| along with the material from the oxidation step in order to reduce the viscosity of that material.

'I'he bottoms from flash tower 25 are withdrawn through line 3l and constitute the desired asphalt.

The soluble material from precipitator 2l passes out from the precipitator at the top thereof through line 38 and heater or cooler 39 and (if desired) reduction valve 40 into a secondary precipitator fil. This secondary precipitator is operated under such conditions as to precipitate any residual oxidized materialor other undesir.- able material which was retained in solution in precipitator 2l. Since precipitator 2| is operated to Vproduce the desired type of asphalt it is impossible to remove all the constituentsundesir= able in a lubricating oil stock. If all these constituents were removed the asphalt would have a high penetration and other undesirable properties. Thus, it is preferred to operate precipitator 2| under conditions adjusted with a view to producing the best possible asphalt and then to Operate secondary precipitator H under such conditions as to remove a further quantity of insoluble matter in order to'produce a lubricating oil of the desired specications.` Further precipita- CLI tion in secondary precipitator 4I is obtained by control of the temperature, pressure and concentration variables as aforementioned. Thus when operating at temperatures immediately below the critical temperature, further precipitation can be obtained by raising the temperature or lowering the pressure. When operating at low temperatures on the other hand further precipitation can be obtained by lowering the temperature. These condtlons can be obtained by control of heater or cooler 39 and/or reduction valve 40 and the degree of precipitation to be obtained in precipitator 4| is that necessary to produce a lubricating oil of the desired specications.

The insoluble material from precipitator 4l passes out of the base thereof through line 42 and (if necessary) heater 43 into a flash tower 44 which may be heated at its base by heating coil 45. The propane or other normally gaseous hydrocarbon vapors pass overhead through valve 46 to the vapor recovery system hereinbefore described.

The material from the base of this tower is in general neither al good asphalt nor a good lubricating oil and it is preferred to recycle this material to the process for further oxidation whereby the bulk of it is converted into asphalt and any small amounts of desirable lubricating oil constituents contained in it will be returned.

to the process and ultimately find their way into the nished lubricating oil. The material from the base of flash tower 44 may be returned through line 41, heater 48 (which may often be omitted) and valve 49 into the original oxidizer I3. However, it is sometimes the case that this recycled stock will need rather different oxidation conditions than does the original feed and in this case the n recycled stock may be introduced through valve 50 and vspray 5I into a second oxidizer 52 supplied with air or other oxidizing agent near its base through line 53. In either case the material from 'the oxidation step finds its way into surge tank I8 and is returned to the DIOCSSS.

The soluble material from secondary precipitator 4i, passes out of the top of the precipitator through line 54, is heated if required in heater 55 and passes through valve 56 into flash tower 51 which may suitably be heated at its base by heating coil 58. The propane or other normally gaseous hydrocarbon vapors from flash tower 51 pass overhead through valve 59 into the recovery system hereinbefore described and the refined lubricating oil passes out of the base of the tower through line 60. As previously mentioned this refined lubricating oil may be subjected to further refining steps such as dewaxing, acid treating, clay treating, etc.

I prefer, however, to conduct these further treating steps in the presence of the propane or other normally gaseous hydrocarbon.4 When operating in this manner valve 56 is closed and valve i is open. Heater 55 is replaced by a cooler or by a flash chamber wherein selfrefrigeration is secured by evaporating a portion of the propane. The propane solution is then pumped by pump 62 through valve 63 and filter press 64. This filter press may be of any conventional type, either batch or continuous. Wax is removed through line 65. In general the temperaturerof the dewaxing step should be from -20 F. to 60 F. and this temperature may suitably be obtained by ashing oir a portion but not all of the propane-or other normally gaseous hydrocarbon.

If the oil used in the process does not contain wax, lter 64 may be by-passed by closing valve 63 and opening valve 66.

In either case the next step may suitably be an acid treating step which is shown as conducted in counter-current treating tower 61. The temperature of this acid treatment may suitably be as low as the dewaxing temperature or as high as 50 F., but I find that highly superior results can be obtained by the use4 of relatively low temperatures (under about 50 F.) and by conducting the acid treating in solution in propane or other light hydrocarbon. The presence of the light hydrocarbon greatly improves the ease with which sludge can be withdrawn. The material from filter 64 or by-pass valve 66 may be heated if desired in heater 68 and then introduced into acid treating tower 61 through valve 69. The acid and sludge are removed through line and may be recycled to the acid introduction line 1| or puried and recycled, but these steps are conventional and are therefore not shown. If acid treating is not required valve 69 can4 be closed and valve 12 opened. In either case the next step may suitably be the removal of propane or other normally gaseous hydrocarbon which may be accomplished in flash tower .13 provided with reduction valve 14, valve (leading into the vapor recovery system) and heating coil 16. The oil from the base of flash tower 13 may then suitably be introduced through line 11 into clay percolator 18 from the base of which the finished lubricating oil is removedl `features of my invention.

I claim: 1. A method of refining a hydrocarbon lubricating oil stock containing constituents of relatively high 'viscosity index and constituents of relatively low viscosity index, which comprises contacting said stock with a gas containing free oxygen under conditions corresponding in eiect to an oxidation temperature of about 300 F. to about 400 F. and an oxidation time of about 30 hours to about 200 hours whereby a substantial portion of said constituents of relatively low Viscosity index are converted into oxidation products insoluble in a light hydrocarbon of the class hereinafter defined and under the conditions hereinafter defined, whereby said constituents of relatively high viscosity index are not converted into oxidation products and whereby the materials resulting from said oxidation step which are soluble in a light hydrocarbon of the class hereinafter dened under the conditions hereinafter defined have a viscosity index at least about 10 Dean and Davis units higher than the Viscosity index of said stock, contacting the lmaterial from the aforementioned o xidation step with from about two to about ten times its own volume of a liquefied light hydrocarbon of the class consisting of ethane, propane, isobutane and butane I at a temperature below the critical temperature of said light hydrocarbon and within about F.

of the critical temperature of -said light hydrocarcipitated, and removing said oxidized constituents.

2. A method according to claim 1 in which sai l liqueiied light hydrocarbon is propane.

3. A method according to claim 1 in which the step of contacting said stock with a gas containing free oxygen is carried out in the presence of ferric chloride.

4. A method according to claim 1 in which the contacting step for precipitating oxidized constituents is conducted at a temperature below, but not more than about 50 F. below, the critical temperature of said liqueed light gaseous hydrocarbon.

5. A method for the rening of a lubricating oil stock containing constituents of relatively high viscosity index and constituents of relatively low viscosity index which comprises contacting said stock with a gas containing free oxygen at an elevated temperature in the presence of ferric chloride for a period of time sufficient to convert a substantial quantity of said constituents of relatively low viscosity indexinto oxidation products without converting said constituents of relatively high viscosity index into oxidation products, the oxidation being suiciently drastic to raise the viscosity index of the unconverted part of the stock at least ten Dean and Davis units above the viscosity index of the stock, contacting the material from the aforesaid oxidation step with .from about two to about ten times its own volume of a liquefied hydrocarbon selected from the group consisting of ethane, propane, isobutane, normal butane and the corresponding olenic hydrocarbons at a temperature between the critical temperature of said'hydrocarbon and a temperature about 100 F. below the critical tern-l perature of said hydrocarbon whereby said oxidized constituents are precipitated, and removing said oxidized constituents.

6. A method according to claim in which the -oxidation temperature is about 250 F. to about 7. A method for the refining of a lubricating oil stock and for the production of asphalt from non-asphaltic constituents of said stock, comprising drastically oxidizing said stock, contacting the material from the oxidation step with a condensed normally gaseous hydrocarbon to precipitate an asphalt and to dissolve the remaining constituents of said materialLremoving said precipitated asphalt, precipitating a further quan- Y tity of material from the solution of said remaining constituents without precipitating the desired lubricating oil constituents, removing the material thus precipitated, re-oxidizing said last-mentioned material, recycling the products of the re-oxidation step to said contacting step, and removing the residual normally gaseous hydrocarbon from said desired lubricating oil constituents.

8. A method according to claim 'I in which at least one of said precipitation steps is conducted at a temperature within about 80 F. of the critica1 temperature of said normally gaseous hydrocarbon. Y

9. A method according to clairn'7 in which at least one of said precipitation steps is conducted at `a temperature at least about F. below, an'cl not more than about 80 F. below, the critical temperature of said normally gaseous hydrocarbon.

10. A method according to claim '7v in which the second precipitation step is conducted at a temperature below, but not more than about 50 F. below, the critical temperature of said normally gaseous hydrocarbon.

11. A method for thereningf of alubricating oil stock and for the production of asphalt from non-asphaltic constituents of said stock, comprising drastically oxidizing said stock, contacting'the material from the oxidation step witha condensed normally gaseous hydrocarbon to precipitate an asphalt and to dissolve the remaining constituents of said material, removing said precipitated asphalt, precipitating a further quantity of material from the solution of said remaining constituents without precipitating the desired lubricating oil constituents, removing the material thus precipitated, recycling said last-mentioned material to said drastic oxidation step, and removing the residual normally gaseous hydrocarbon from said desired lubricating oil constituents.

12. A method according to claim 11 in which at least one of said precipitation steps is conducted at a temperature within about 80 F. of the critical temperature of said normally gaseous hydrocarbon.

13. A method according to claim l1 in which at least one of said precipitation steps is conducted at a temperature at least about 10 F. below, and not .more than about 80 F. below, the critical temperature of said normally gaseous hydrocarbon.

14. A method according to claim l1 in which the second precipitation step is conducted at a temperature below, but not more than about 50 F. below, the critical temperature of saidA normally gaseous hydrocarbon.

CHESTER. E. ADAMS.

CERTIFICATE oF CORRECTION.

Patent No. 2,070,567. February 15, 19E

CHESTER E. ADAMS.

It is hereby certified that error appears in the printed specificatie: of the above numbered patent requiring oorrectionfas follows: Page 1, first column, line 20, after the word "has" insert been; and second column, line 2-3, for "difficulty" read difficultly; page 4, first column, line' lO, for "oondtions" read conditions; and second Column, line 40, for` "oetrain" read certain; page 5, first column, line 16, Claim 4, strike out "gaseous"; and that the said LettersY Patent should be read'- with these corrections therein that the same may conform to the record of the case in the Patent Office.V r

Signed and sealed this 30th day of Marclffi,A. D. 1957".

Henry Van Arsdal'e (Seal) Acting Commissioner` of Patents. 

